I know in case of csdid if I run the following regression then I'll get the ATT.
Code:

csdid ln_wage, ivar(county) time(year) gvar(policy_year) agg(event)
estat simple

estat simple
Average Treatment Effect on Treated
------------------------------------------------------------------------------
             | Coefficient  Std. err.      z    P>|z|     [95% conf. interval]
-------------+----------------------------------------------------------------
         ATT |  -.0033592     .00675    -0.50   0.619    -.0165889    .0098706
------------------------------------------------------------------------------


However, I have tried several methods to find the ATT like the one I get in CSDID when I apply the did_imputation but I've not been successful to do so. Would you kindly guide me how I can end up getting the ATT in case of did_imputation ?

Code:
ssc install did_imputation, replace

did_imputation ln_wage county year policy_year, autosample horizons(0/5) pretrend(5) minn(0)

Would really appreciate your valuable input!